Booklets, like mail order advertising brochures, are typically mass-produced in printing plants by apparatus which includes a signature collating conveyor chain formed by interconnected inverted V-shaped chain links over which sharply folded sheets or signatures are sequentially draped in stacked relation to form booklet bodies. The conveyor chain moves over a path passing by spaced signature feeding stations which include signature feeding means for successively draping and stacking the sharply folded pre-printed signatures over the conveyor chain, with the crotch of each signature fold resting on or overlying the apices of the chain links. Some of the chain links include horizontally projecting lugs (to be referred to as signature positioning and pushing means) which engage the trailing edges of the various stacks of signatures draped over the chain, to position and align the same. The conveyor moves the completed stacks of signatures on the conveyor chain to a stitching or binding station which commonly applies binding staples through the folds of the stack of signatures to form bound booklets. The bound booklets are then commonly delivered to a trimming station and then to a labeling station where mailing labels are applied which are pre-printed or printed on line with the desired addressee information.
When the booklets involved are advertising booklets which desirably contain order forms on the inside thereof, it is desirable to incorporate on the order forms in the booklets the name and address of the addressee thereof so that the person ordering the merchandise involved does not have to bother printing his name and address on the order form. Thus, U.S. Pat. No. 3,819,173 to Anderson et al, granted June 25, 1974 discloses computer controlled booklet-making apparatus which includes a printing station which prints addressee information on a pre-printed order form card which is then inserted within each stack of signatures on the conveyor chain prior to its application to the binding and labeling stations.
The desirability of using an ink jet printing head for printing mail order form addressee information directly on a moving sheet of paper or the like having a to-be-printed or pre-printed order form thereon and other printing to form a mail order advertising booklet is disclosed in U.S. Pat. No. 3,911,818 to MacIlvaine, granted Oct. 14, 1974. The ink jet printing head referred to in this patent provides ink jet nozzles from which ink can be selectively directed upon a printing surface in a direction transverse to the direction of movement of the sheet of paper involved. By controlling the position of the ink jets issuing from these nozzles at any instant of time and the timing of the position changes thereof in relation to the speed of movement of the sheet of paper the desired letters and numbers are formed to produce the desired addressee information upon the spaces on the order form provided therefor. While the MacIlvaine patent discloses the sheet of paper as a single moving web of paper, it is manifest that the moving web can be replaced by any moving sheet of paper, like a signature draped over a conveyor chain which advances the signature to the various stations in a booklet-making line. The present invention applies to such a printing operation.
Various types of ink jet printers are presently being used to print addressee information on a moving conveyor chain carried signature forming part of a mail order advertising booklet. Thus, one type of known printing head manufactured by the Mead Corporation of Dayton, Ohio uses a separate vertically oriented ink jet nozzle for each segment of the numbers and letters involved. The separate nozzles are very small and are aligned in closely spaced relationship along a line transverse to the direction of movement of the conveyor chain. The pattern of ink issuing from the nozzles at any instant is varied in synchronism with the chain speed to form the desired imprint.
The aforementioned McIlvaine patent and U.S. Pat. No. 4,121,818 to Riley et al, granted Oct. 4, 1978, disclose the previously described form of ink jet printing head including one or more nozzles oriented to direct what is disclosed in the drawings of these patents as a deflectable, generally horizontally extending ink jet on a generally vertically extending face of a web of paper or conveyor chain carried signature. In such case, a single ink jet can form the various vertical segments of any letter or number by controlling its deflected ink ejecting position.
In either case, to obtain the best printing results, it is important to stabilize and align the movement of the web or signature past the ink jet printing head involved, so that the information printed thereon will be properly aligned on the order forms (and labels where the labels are similarly printed "on-the-fly"). Various means have been heretofore utilized for stabilizing the motion of the signature as it is moved past the ink jet printing heads. While these means have generally provided acceptable results, they have left much to be desired. Thus, longitudinally spaced pressure rollers have been proposed to press the upstanding folds at the juncture of vertically extending signature panels against the apices of the chain links. Pressing the folded signatures during a printing operation against the apices of the conveyor chain links is unsatisfactory if the apices of the conveyor chain links do not remain perfectly aligned in longitudinal and lateral directions. Generally, the apices of the chain links do not have a sufficiently consistent elevation and lateral position that one would want to use the upper surface as a guide for the path of movement of the signatures during a printing operation.
Where the printing head is to direct the ink jets in a generally vertical direction upon a signature surface, the signature panels draped over the conveyor chain must be raised to a horizontal position as is required when using the Mead printing unit previously described. We have carried out experiments with various means for stabilizing the position of the raised panels of such a signature by longitudinally spaced rollers and other pressure applying means pressing down on the raised signature panels supported on a horizontal table while the still vertically oriented fold thereof remains on the conveyor chain. It was found that, frequently, horizontal or lateral shifting of the signatures took place as the leading edges of the signatures first passed under the first pressure roller or other pressure applying means. This lateral shifting of the signatures caused the printing to be mis-aligned with the order form spaces provided therefor.
It is the object of the present invention to improve the quality of the printing achieved by use of ink jet printing heads printing on moving conveyor chain-supported signatures by providing the best possible alignment of the printing on the signatures.